The Cellular Digital Packet Data (CDPD) Specification allows for a mechanism that restricts registrations on a specific CDPD channel. A Channel Capacity flag is sent as part of the Channel Identification Message, which is broadcast on the forward channel at regular intervals. An M-ES (Mobile End-System) seeking CDPD service, and noting that this flag indicates full, will not attempt to access this channel. Instead the M-ES will either wait and keep examining the forward channel for changes in the Channel Identification Message, or will seek an alternative channel for its CDPD needs, according to the channel acquisition algorithm it uses.
The protocol used on the airlink for the CDPD Specification is DSMA/CD (Digital Sense Multiple Access with Collision Detection). A closely related protocol, CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is used on many wired networks. To analyze the effects of fading and noise on the channel, the traditional approaches one may attempt, based on a natural evolution of the extensive work that exists in the literature on CSMA/CD, fail. A method of analysis that incorporates the fundamental ingredients of cellular channels i.e. fading and noise, has to be developed.
The present invention uses a method of analysis that incorporates the effects of fading and noise to derive an algorithm to set the Channel Capacity Flag.
Elementary types of congestion control such as those which consider the number of mobiles using the system at a particular time make inefficient use of the available channel capacity.